1) Field of the Invention
The present invention relates to compositions for the preparation of dosage-form active vitamins D.sub.3 in which the active vitamins D.sub.3 have superb stability.
2) Description of the Related Art
Active vitamins D.sub.3 such as 1.alpha.-hydroxyvitamin D.sub.3 and 1.alpha.,25-dihydroxyvitamin D.sub.3 are known as excellent therapeutic drugs for rickets, osteomalacia and the like. These active vitamins D.sub.3 are however very unstable substances, so that they undergo decomposition even at room temperature and cannot be stored for long time even when prepared into dosage forms.
As their stabilization method, it has heretofore been known, for example, to form each active vitamin D.sub.3 into a composition by dissolving it in triglyceride (Japanese Patent Application Laid-Open No. 130,905/1977), to add an amino acid as a stabilizer (Japanese Patent Application Laid-Open No. 17/1987) or to form it into a composition by dissolving the same in a propylene glycol fatty acid ester (Japanese Patent Application Laid-Open No. 54323/1988).
These methods are however not fully satisfactory. There has hence been a desire for the development of a still better method for the stabilization of active vitamins D.sub.3.